1970 Coupe 472 Vacuum Lines
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500, 472, 425, 368 Discussion, 1970 Coupe 472 Vacuum Lines in Cadillac Engine Technical Discussion; 1970 Coupe Deville, 472 Stock. Full Tuneup was done last summer but the car is not running to full potential. ...
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    Cristofo's Avatar
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    1970 Coupe 472 Vacuum Lines

    1970 Coupe Deville, 472 Stock.

    Full Tuneup was done last summer but the car is not running to full potential. I'm still unsure of how the vacuum is hooked up, so I drew a picture of my current setup. I have a vacuum leak somewhere I just can't find it exactly. I attached 2 pictures, 1 that is the only vacuum diagram you'll find online for these years and the other is the one I drew real quick.

    I have the thermal 3 port switch hooked up correctly, D, C, MT but my question lies more on the Carb side. If you look at my carb straight on from the front of the vehicle, there is a small vacuum port on the left side which is uncapped with no hose connected. The choke pull off diaphram that has 2 nipples is what is confusing me and why would the carb nipple have nothing connected to it here? The back top center vacuum port on the carb is plugged with a golf tee because my electric vacuum switch that was in this line broke. I believe it controlled vacuum depending on engine temp?

    Anyway, i have a hesitation when you step on the gas and you can't put you foot into it when rolling or it bogs and pings. Timing set between 5-7, advance disconnected and hose plugged. The carb has not been rebuilt and looks to be in need of a complete cleaning and rebuild. Anyone else have problems with there vacuum setup and finding any leaks?

    Thanks,
    Chris
    Attached Images

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    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1970 Coupe 472 Vacuum Lines

    Here's a pic of the vac diagram from the factory service manual.



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    Here's a couple of other pics when I was taking mine apart:





    I didn't put it back like it was, I changed the carb out and got rid of the transmission controlled spark thingy and the ported vacuum switch, so all I have for you is the pics I took when it came apart, can't go look now, mines all different.

    Hope this helps. I you have specific questions about where a specific vac line ran, I can continue to look thru my pics.

    chris.

    ----------

    As far as the car running poorly, it sounds like your vacuum advance isn't working. With the timing light connected, when you rev it up, does the timing mark move like it should? Or it could be the carb, specifically the accelerator pump. Do you have good compression? and new points/plugs etc? and the plugs look good?

    Now mind you I'm no mechanic. I can change parts, but I ain't no good at diagnosing.
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    Re: 1970 Coupe 472 Vacuum Lines

    Thanks for this, its a huge help. Looking at these pictures and service manual, I now see that my MT (intake manifold vac on the Carb) needs to be hooked up. In your pic, Its T'd coming from the carb, 1 going down to MT and 2nd hose going to the choke pulloff. Where does the 2nd hose go that comes off the choke pulloff?

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    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1970 Coupe 472 Vacuum Lines

    Crap! I'm not 100% sure where the 2nd hose goes. I've attached a pic, but the hose is disconnected. It either went to the vacuum "T" on the firewall (port coming straight out) or went to the vacuum storage tank on the passenger fenderwell. I'm leaning that it goes to the vac T on the firewall, but not sure. I labeled all the hoses when I took them apart and can't read what's written in the pic..........



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    Post your question here: http://forums.cadillaclasalleclub.or....php?board=2.0

    There are tons of folk who have original '70s that can help. I'm not near where I can read what I labeled on that vac line. Bummer. Sorry. I'll monitor this for more ?s, but not sure if I'm your answer........
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    Re: 1970 Coupe 472 Vacuum Lines

    This is great I'm going to take a look soon and see if I can do some switching. I'll let you know how I make out.

    thanks again!

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    Re: 1970 Coupe 472 Vacuum Lines

    I hooked up everything as close as possible but I cannot find an empty vacuum nipple on the firewall/fender for the 2nd port of the choke pulloff. Wonder if I need a T connector back on that vacuum connection in your last picture top almost center of the photo. It looks like you have a T connector but mine did not. I may have to try that setup and see how it works out, currently idle and takeoff is a little rough but midrange throttle is smooth and strong. I cannot slam the pedal or it just bogs down and starts to run awful. I honestly think there is a miss to add to the mix as well.

    Can I bypass and cap everthing and just run directly from the Carb to the Distributor advance? My next purchase will be a Petronix or Accel points eliminator kit and I want to redo the spark plugs but Im extremely eager to wrap up this vacuum setup.

    Thanks for your help, we're almost there.
    Chris

  8. #7
    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1970 Coupe 472 Vacuum Lines

    Going thru my pics again, it appears the "T" on the firewall goes to the cruise control transducer. It appears the 2nd vac line coming of the choke pull off goes to the vacuum canister on the passenger fenderwell. Still looking for a pic.

    ----------

    Definitely doesn't go to the "T" on the firewall. The hose size is larger than what comes off the choke pull off.

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    Here is a pic of the vacuum canister on the fenderwell. In between the heater hoses and the red duct taped end of the a/c lines. Now I'm 90% sure it went there. If I could get back to the shop and look for those vacuum hoses, I could read the tape to tell for sure.

    Regarding your question of routing around the ported vacuum switch (PVS), yes you can. The purpose of the PVS is to allow ported vacuum only to get to the vacuum advance once the engine is up to a certain temperature. I believe its an emission control device. On my rebuild, I plugged the hole where the PVS was and ran ported vacuum (not straight manifold vacuum) to the distributor vac advance.



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    I bought a replacement distributor from MTS. I'm pretty sure its an MSD. They were very helpful. They offer performance items for the 472/500 engines.

    http://www.500cid.com/index.htm

    Here's a pic of the motor now:

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    Re: 1970 Coupe 472 Vacuum Lines

    Wow the motor looks awesome in the final pic, I would like ours to look that way someday.

    In regards to the where the 2nd hose off the choke goes, I think I would agree and now that makes sense. I currently have it hooked up to the fender and the vacuum hose coming from underneath the air cleaner assembly was hooked up to this fender canister prior to me switching it yesterday. I temporarily plugged the air cleaner hose since now that is the odd man out. Do you know where that hose goes as well?

    Once I get it running the way I like and have the factory vacuum setup correctly, I'm taking a ton of pictures and then switching to your setup

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    Re: 1970 Coupe 472 Vacuum Lines

    Just picked up an Accel Eliminator kit, finally going to get rid of the points/condenser setup as well. I'm sure I'll end up with a new thread but the setup seems pretty easy, im leaving the stock coil for now so I won't touch the resistor. Only thing I noticed they say in the instructions not to use with copper core spark plug wires. I can't see that being a big issue...

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    Re: 1970 Coupe 472 Vacuum Lines

    The hose that comes off the bottom of the air cleaner goes to the vacuum check valve on the firewall. In my pic, the red duct tape is covering where the outlet was-it connects there, mine is broke, thus the duct tape over the opening. It is supposed to go there, but I don't even have mine hooked up to anything. My air inlet in the air cleaner is always open and that's ok w/ me.



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    Just a heads up on eliminating the points/condenser. The voltage going to the coil is stepped down to 7 or 8 volts via a resistor wire coming from the ignition switch. It is not a full 12 volts. If your kit needs 12 volts, you'll have to abandon the resistor wire and find "keyed" 12 volts elsewhere. I got mine under the dash (found the pink 12 gauge wire coming off the ignition switch (before it goes to the resistor wire)) and ran it thru the firewall to the + side of the coil. You'll see two wires merged into one on the + side of the coil. The resistor wire brings stepped down voltage from the switch, the other wire brings 12 volts to the coil (from the starter solenoid) while the starter is cranking.

    Here's a pic of the two wires. If you look closely, one is covered with a "braided" type covering, the other is a standard type wire. The braided wire is the resistor wire.



    Here's another pic of the wire nearing the firewall. I was hoping the resistor wire started in the engine compartment, it did not, it started under the dash.



    If you don't need a full 12 volts to drive your new ignition, you'll be fine, if you need a full 12 volts, you have more work to do. Ugh.
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    Re: 1970 Coupe 472 Vacuum Lines

    Everything you posted is extremely helpful, I will install the kit tomorrow at lunchtime and fix the air cleaner vacuum hose as well. I believe the Accel kit is good running with the resistor wire (lower voltage) but I will find out for sure tomorrow. I will take a few good pics tomorrow of my setup to see if I missed any lines/hoses.

    You have a 70 Deville convertible right?

    Thanks!!
    Chris

  13. #12
    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1970 Coupe 472 Vacuum Lines

    yep and I love the 1970 styling!

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    Re: 1970 Coupe 472 Vacuum Lines

    Quote Originally Posted by chrisntam View Post
    yep and I love the 1970 styling!

    LOVE IT, I was looking for the 70 specific year for about 10 years prior to picking up my coupe hardtop. Just something about them that I love so much, even though I love Caddys in general. I want one from every year basically but I had to have the 70. I'm waiting impatiently to get to the car tomorrow. We park it at my dads building so its not like going out to the garage to tackle something you have been thinking about all day.

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    Re: 1970 Coupe 472 Vacuum Lines

    I tried to install the Accel Points Eliminator on my lunchbreak but it turned out to be a PITA. Nothing is complex, but the room you have to work sucks. With the Accel kit, the instructions don't mention that once you install the module there is no room to install the shutter wheel bolts that connect to the rotor. I had to lay the yellow module in their loose as I tried to install the shutter wheel....Anyway I have everything installed, I just need to wire it up, check timing and take a testdrive.

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    chrisntam is offline Cadillac Owners Fanatic
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    Re: 1970 Coupe 472 Vacuum Lines

    Progress!! Hope it fires right up!

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